<![CDATA[Shallot productivity is frequently constrained by low nutrient use efficiency and declining soil quality caused by continuous application of inorganic fertilizers. This study aimed to evaluate the effects of humic acid and NPK 16:16:16 fertilizer, as well as their interaction, on the growth and yield of shallot (Allium ascalonicum L.). The experiment was arranged in a factorial Randomized Block Design with two treatment factors and three replications. The first factor was humic acid dosage consisting of 0, 1.5, 3, and 4.5 g plant ⁻ ¹, while the second factor was NPK 16:16:16 dosage consisting of 0, 15, 30, and 45 g plant ⁻ ¹. The results revealed that both humic acid and NPK 16:16:16 significantly affected several physiological and yield parameters of shallot plants. Significant interactions were observed on plant height at 3 weeks after planting, leaf nitrogen uptake, leaf area index, and fresh bulb weight. The combination of 45 g plant ⁻ ¹ NPK and 4.5 g plant ⁻ ¹ humic acid produced the highest fresh bulb weight of 74.76 g plant ⁻ ¹. Humic acid application enhanced nutrient uptake efficiency, improved soil nutrient availability, and stimulated plant physiological activity, while NPK fertilizer supplied essential macronutrients required for optimal bulb development. The novelty of this study lies in demonstrating the synergistic interaction between humic acid and NPK 16:16:16 in improving shallot productivity under low-organic-matter soil conditions. Therefore, the combined application of 45 g plant ⁻ ¹ NPK 16:16:16 and 4.5 g plant ⁻ ¹ humic acid is recommended as an effective and sustainable fertilization strategy for shallot cultivation.]]>
